1. Field of the Invention
The present invention relates to a plastic bristle for toothbrushes and to a toothbrush provided with such bristles.
2. The Prior Art
Toothbrushing is generally known for its cleaning function, the remove food debris and plaque; but, it also massages the gingival tissue increasing keratinization which enhances gingival health, and in conjunction with an abrasive dentifrice removes the stained pellicle on the tooth surface to enhance tooth whiteness. The ability of a toothbrush to perform these functions is related to the size of the head, the distribution of the bristle tufts, the properties of the individual bristles as determined by their material of construction plus their size and shape, the bristles per tuft, and the configuration of the tufts themselves. In general the more surface area of bristle applied by the user to the tooth and gingival surface, the more plaque and debris that will be removed, the greater the massaging effect and the greater the removal of stained pellicle.
Today, virtually all commercial toothbrush bristles manufactured in the U.S. are made of polyamide (i.e. nylon). The stiffness of a nylon bristle is primarily related to the modulus i.e. resistance to bending of the particular nylon, and the filament diameter (i.e. thickness) and trim length. The stiffness of the nylon bristle, the number of bristles comprising a tuft, and the number of tufts in a brush are major variables involved in the classification of a toothbrush as "soft", "medium" or "firm"/"hard". Scientific studies have shown that the "softer" the brush the less it will abrade the soft gingival tissue surrounding the tooth, which abrasion can lead to not only gingival recession, but also abrasion of the cervical area of the tooth itself. M. Pader, Oral Hygiene Products and Practice, Marcel Dekker, Inc., New York (1988), pages 169-170.
In addition to the "softness" of a brush, it is commonly accepted that one of the most important sources of oral abrasion caused by toothbrushing is related to the finish of the tip of the bristles. The end of a bristle may have sharp edges after trimming, as well as small ridges and burrs. By end rounding, the ends of the bristles are smoothed to minimize the possibility of incremental abrasion from such edges, ridges and burrs.
British Patent 490,124 and Swiss Patent CH 049277 disclose a solution to providing more bristle surface area by bundling or packing individual fibers together to form the tufts of toothbrushes. In the British Patent the tufts are held together by a synthetic resin, and within a tubular rod as in the Swiss Patent. German Patent DE 4417548 further discloses that bristles formed of very fine fibers clad in an elastic material to form the tufts further enhance cleaning while being softer to avoid injury to the gums.
There is a continuing need in the toothbrush art for bristles having more surface area to enhance the removal of plaque and food debris, while at the same time having a smaller diameter and end rounding, to be softer and reduce toothbrush abrasion.